Hi,

How much time would one normally expect (in a sealed system) before
all the air is out?

I had a new CH system fitted over two weeks ago and I am still having
to bleed some of the radiators every couple of days. The pressure is
not dropping noticably so I don't think there is a leak anywhere!

I always bleed the rads when the CH is off (Does this still apply in a
sealed system?).

TIA, Mark

Each time you bleed, I assume you are topping up again through the
filling loop?

Each time you top up you introduce more airated water to the system.

What you should notice is that each time you bleed it takes slightly
less time to let the air out.

I'd say you should be getting very close to it now.

On 8 Mar 2005 07:18:25 -0800, "kmillar" wrote:

Each time you bleed, I assume you are topping up again through the
filling loop?

No. As the pressure has not dropped I did not bother. Maybe this is
wrong but I'm no expert at this.

Each time you top up you introduce more airated water to the system.

What you should notice is that each time you bleed it takes slightly
less time to let the air out.

I'd say you should be getting very close to it now.

I've not really noticed the time taken to bleed the radiators.

Mark

In article ,
Mark writes:
Hi,

How much time would one normally expect (in a sealed system) before
all the air is out?

Most of it should be out in a few days. You might still hear the
odd bubble going around the system for a few weeks. I last topped
mine up about 2 years ago, and I still occasionally hear a bubble
force its way through one of the flow restrictors.

I had a new CH system fitted over two weeks ago and I am still having
to bleed some of the radiators every couple of days. The pressure is

Is this because they are getting cold at the top, or just because
you can still get some air out?

not dropping noticably so I don't think there is a leak anywhere!

Leaks are two-way affairs. Often air will leak in faster than water
leaks out, even though the system is pressurised. You might not see
water leaking out as it can evaporate as fast as it leaks when system
is warm. Leaks are often more 'visible' when system is cold.

If you are removing air from the system and it isn't being replaced,
I would expect the pressure to drop due to the bleeding alone.
Do you know if an inhibitor was added?

I always bleed the rads when the CH is off (Does this still apply in a
sealed system?).

When the system is cooled down, much of the air can redissolve in
the water. I would speculate the best way to bleed it is to crank it
up to maximum water temperature (when the maximum amount of air will
come out of solution) and then bleed this before it cools and
redissolves. I never heard anyone say to only bleed when CH is off.

--
Andrew Gabriel

On Tue, 8 Mar 2005 15:22:31 +0000 (UTC),
(Andrew Gabriel) wrote:

In article ,
Mark writes:
Hi,

How much time would one normally expect (in a sealed system) before
all the air is out?

Most of it should be out in a few days. You might still hear the
odd bubble going around the system for a few weeks. I last topped
mine up about 2 years ago, and I still occasionally hear a bubble
force its way through one of the flow restrictors.

I had a new CH system fitted over two weeks ago and I am still having
to bleed some of the radiators every couple of days. The pressure is

Is this because they are getting cold at the top, or just because
you can still get some air out?

Both.

not dropping noticably so I don't think there is a leak anywhere!

Leaks are two-way affairs. Often air will leak in faster than water
leaks out, even though the system is pressurised. You might not see
water leaking out as it can evaporate as fast as it leaks when system
is warm. Leaks are often more 'visible' when system is cold.

Are you saying that I may have a leak? If so how can it be found
since most of the pipes are under the floor?

If you are removing air from the system and it isn't being replaced,
I would expect the pressure to drop due to the bleeding alone.
Do you know if an inhibitor was added?

I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)

I always bleed the rads when the CH is off (Does this still apply in a
sealed system?).

When the system is cooled down, much of the air can redissolve in
the water. I would speculate the best way to bleed it is to crank it
up to maximum water temperature (when the maximum amount of air will
come out of solution) and then bleed this before it cools and
redissolves. I never heard anyone say to only bleed when CH is off.

I was told this by an experienced BG heating engineer. It certainly
made a difference on my old gravity system.

Mark

When the system is cooled down, much of the air can redissolve in
the water. I would speculate the best way to bleed it is to crank it
up to maximum water temperature (when the maximum amount of air will
come out of solution) and then bleed this before it cools and
redissolves. I never heard anyone say to only bleed when CH is off.


I was told this by an experienced BG heating engineer. It certainly
made a difference on my old gravity system.

Mark


FWIW. We have a sealed system and I bleed our radiators once a year. I
get them up to temperature, switch the heating off, then bleed the air
out. Since that lowers the pressure I then wait for the system to cool
down and top up to the working cold pressure (1 bar in our case). It
might be a bit of messing around but it's only once a year (we have a
loft conversion with a radiator - it collects all the air so I suppose
we have it easier than normal).

doozer wrote:


FWIW. We have a sealed system and I bleed our radiators once a year. I
get them up to temperature, switch the heating off, then bleed the air
out. Since that lowers the pressure I then wait for the system to cool
down and top up to the working cold pressure (1 bar in our case). It
might be a bit of messing around but it's only once a year (we have a
loft conversion with a radiator - it collects all the air so I suppose
we have it easier than normal).

Also FWIW! In my pressurized system with attic rad it is (both) towel
rads that collect the air - one more (nearest the boiler) than the
other. The ****** plumber who installed the system did not add an
inhibitor. When I asked him during commissioning if he was going to he
said that he didn't bother! Oh my simple minded trust ;-( I have
flushed it twice and added a tube of Fernox (last June) and I'm still
bleeding the *****ing system. I've just ordered some DENC valves to
make my life easier!

Richard

--
Real email address is RJSavage at BIGFOOT dot COM

The information contained in this post
may not be published in, or used by

http://www.diyprojects.info

In article ,
doozer wrote:
FWIW. We have a sealed system and I bleed our radiators once a year

Then something must be wrong.

--
*If vegetable oil comes from vegetables, where does baby oil come from? *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
doozer wrote:

FWIW. We have a sealed system and I bleed our radiators once a year


Then something must be wrong.


Why do you say that? Every now and then a sealed system needs topping
up. That introduces cold water which contains air. It is therefore
reasonable, I think, to expect to have to remove that air once in a while.

If you think there is a specific problem I would like to know more
about what you think it is. Perhaps a very slow leak somewhere?

In article , Mark
writes
I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)

If it was added, the water from the radiators should be straw coloured,
drain a little from a bleed valve to check. If clear, find plumber and threaten
with violence . . .
--
fred

fred wrote:

In article , Mark
writes

I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)


If it was added, the water from the radiators should be straw coloured,
drain a little from a bleed valve to check. If clear, find plumber and threaten
with violence . . .

The water in my Fernox treated system appears to be colourless - if the
colour of the water that emerges when bleeding the rads is anything to
go by - but it does taste horrible tho'!

Richard

--
Real email address is RJSavage at BIGFOOT dot COM

The information contained in this post
may not be published in, or used by

http://www.diyprojects.info

In article , Richard
writes
fred wrote:

In article , Mark
writes

I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)


If it was added, the water from the radiators should be straw coloured,
drain a little from a bleed valve to check. If clear, find plumber and threaten
with violence . . .

The water in my Fernox treated system appears to be colourless - if the
colour of the water that emerges when bleeding the rads is anything to
go by - but it does taste horrible tho'!

Bugger, maybe my straw colour was the beginning of rust, tell me there is
a hint of straw colour in yours, please . . . .

I'm going a bit by the colour of the liquid Fernox I added when I
commissioned the system and the colour of the water when I bled the it. 2
years on and a couple of partial drains later and the colour is getting a bit
darker, so maybe a drain & refresh of fernox is called for.
--
fred

On Tue, 08 Mar 2005 21:04:30 GMT, fred wrote:

In article , Mark
writes
I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)

If it was added, the water from the radiators should be straw coloured,
drain a little from a bleed valve to check. If clear, find plumber and threaten
with violence . . .

It's a greyish colour.

I'm still having to bleed quite a bit of air out of one or more
radiators.

Mark.

In article , Mark
writes
On Tue, 08 Mar 2005 21:04:30 GMT, fred wrote:

In article , Mark
writes
I don't think any inhibitor was added. I'll have to speak to the
plumber (if I can find him:-)

If it was added, the water from the radiators should be straw coloured,
drain a little from a bleed valve to check. If clear, find plumber and threaten
with violence . . .

It's a greyish colour.

I'm still having to bleed quite a bit of air out of one or more
radiators.

That doesn't sound too good, the corrosion product of iron (steel radiators)
in heating systems is black so grey suggests that the process has already
started. This suggest that an inhibitor has not been added. It's difficult to
tell without seeing it but you could do a quick test on the fluid as follows:

Draw off a small amount from a radiator, just 50ml or so, then dilute it 4:1
with clean water to make about a cup full (200ml) drop in a clean steel nail
& leave for 24hrs. If there is any trace of rust on the nail then drain, flush
(with just water) & refill with correct level of inhibitor.

The test is a close copy of an earlier post of mine. If the nail has any hint
of rust then kick arse on the installer. Polite approach probably the best,
asking if he added an inhibitor (giving him the chance to say he forgot). If
answer is no then quote the British Standard for domestic central heating
systems to him stating that a chemical flush followed by clean water flush
(hot & cold) followed by filling with water and inhibitor is required, it's BS
5449. I haven't read it but I bet it will say something like that :-).

There are other possibilities but perhaps post back again with the results
of your test, maybe best in a new thread as this one has sunk down the
group so much that I only caught your post by chance.

HTH
--
fred

On Tue, 08 Mar 2005 15:22:31 +0000, Andrew Gabriel wrote:

In article ,
Mark writes:
Hi,

How much time would one normally expect (in a sealed system) before
all the air is out?

Most of it should be out in a few days. You might still hear the
odd bubble going around the system for a few weeks. I last topped
mine up about 2 years ago, and I still occasionally hear a bubble
force its way through one of the flow restrictors.

I had a new CH system fitted over two weeks ago and I am still having
to bleed some of the radiators every couple of days. The pressure is

Is this because they are getting cold at the top, or just because
you can still get some air out?

not dropping noticably so I don't think there is a leak anywhere!

Leaks are two-way affairs. Often air will leak in faster than water
leaks out, even though the system is pressurised. You might not see
water leaking out as it can evaporate as fast as it leaks when system
is warm. Leaks are often more 'visible' when system is cold.

If you are removing air from the system and it isn't being replaced,
I would expect the pressure to drop due to the bleeding alone.
Do you know if an inhibitor was added?

I always bleed the rads when the CH is off (Does this still apply in a
sealed system?).

When the system is cooled down, much of the air can redissolve in
the water. I would speculate the best way to bleed it is to crank it
up to maximum water temperature (when the maximum amount of air will
come out of solution) and then bleed this before it cools and
redissolves. I never heard anyone say to only bleed when CH is off.

With a sealed system you're right. With an incorrectly installed vented
system it is possible let air in when you open a bleed point. Hence the
advice.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html